A suicide bomber plowed a motorcycle into a group of police escorting a protest rally in the eastern Pakistani city of Lahore on Monday, killing at least 11 people and wounding nearly 60 in an attack claimed by a breakaway Taliban faction.

The blast ripped through the crowd of hundreds of pharmacists, who were protesting new amendments to a law governing drug sales. Two senior police officers, including a former provincial counterterrorism chief, were among those killed, police said.

Sameer Ahmad, the Lahore deputy commissioner, said at least 11 people were killed and 58 wounded, including nine who were in critical condition.

Live TV registered a loud bang and showed smoke and fire billowing up as people ran away, some of them carrying the wounded.

“We just couldn’t understand what happened,” Tufail Nabi told local Geo News TV. “It was as if some big building collapsed,” he said as he limped away.

A group called Jamaat-ul-Ahrar claimed the attack in a text message, saying it was revenge for Pakistani military operations against Islamic militants in tribal regions along the Afghan border.

The group, which claimed a number of large attacks last year, is one of several splinter factions from the Pakistani Taliban, which has repeatedly targeted security forces and religious minorities. In recent years, Pakistan has launched several offensives against the Taliban and other Islamic militants in the tribal regions.

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